Usually, an air bag system is mounted in a car as a subsidiary device to a seat belt and the air bag system comprises an air bag module having an air bag, a gas generator, a pat cover, a front impact sensor, a rotary contact switch, and a calculator.
Generally, the air bag module of the air bag system is installed in a steering wheel, so that a cavity is formed in a hub of a steering wheel for mounting the air bag module therein.
Therefore, steering wheels are manufactured differently according to a mounted air bag and a nonmounted air bag.
The air bag system is provided optionally in a vehicle since the system is expensive, so that there are many vehicles in which an air bag system is not installed.
General construction of a steering wheel for a nonmounted air bag is shown in FIG. 1 according to the prior art.
As shown in FIG. 1, a steering wheel 20 is made of hard materials and the steering wheel is mounted at an upper end of a steering shaft 10. A hub cover 30 made of a hard material is fixed at the center of the steering wheel 20.
In a car accident, the driver's head collides with the hub cover 30. However, the contact area of the driver's head and the steering wheel is small and the repelling force from the steering wheel is large, so that the steering wheel causes major injuries to a driver because the steering wheel 20 and the hub cover 30 are made of hard materials as described above.
Accordingly, it is an object of the present invention to provide a steering wheel having a collapsible hub used for a nonmounted air bag in a vehicle in which the hub of the steering wheel is so constructed as to absorb the impact of a driver in a car accident.